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Getting Rid of Transformer Hum

I just picked up a Proceed AMP5 the other day. Upon hooking it up to a power cord, I noticed an annoying pulsating hum that sounds like a lightsaber match in Star Wars. This hum is coming straight from the amp, not the speakers, so it's not ground loop. There is nothing hooked up to the amp besides the power cable. What's interesting is that the amp is even though there is a standby mode, the amp was definitely turned off!

I noticed, though, that the hum got louder as the voltage from my wall dropped below 115-ish. Lowest it got to was 109 when everything was turned on, including a halogen lamp. Well, I turned off the lamp and all the lights in the house, and unplugged them -- helped the voltage drop but didn't eliminate the hum.

Am I completely lost on this amp? Or is there a way to take care of this problem without investing thousands more on some power regenerator? Another poster mentioned a similar problem solved by tightening a "chassis ground screw", but I have no idea what/where that is.

Help!
rakuennow
ngjockey
1,042 posts
 
Core saturatuation caused by DC. Period.

Question is whether it's coming from inside the house or outside.

The irony is that transformers are great at eliminating DC.

http://diyparadise.com/dablok.html
Post removed 
rakuennow OP
81 posts
 
The irony mentioned by Ngjockey is what confused me. I've since read plenty of articles like the one Tvad provided (btw, thank you), on magnetostriction and DC. However, the consensus seems to be that all quality Toroids and modern electric equipment should be sufficient at removing DC. The ones proposing DC as a main problem all seem to be selling something. Still, there are people as there are here, in this thread, that says an isolation transformer, or a device like the Channel Islands Audio XDC-2 solved all their problems.

So here, I'm at crossroads with my wallet since I really don't want to spend colossal amounts of money (to me) on all these devices, which in my opinion, are being marked up ridiculously.

I'm entertaining, though, one alternative option. I could try to sell my Panamax "line conditioner", and buy a used voltage regulator, which should take care of magnetostriction, and to my underestanding, DC as well. Are there any opinions on this?
i.e. Monster AVS 2000, PS Audio Power Plant...

I'll probably end up getting the CIA XDC-2 if it turns out the Monster would be insufficient...
Post removed 
ngjockey
1,042 posts
 
Sorry if that confused you. The irony is that transformers hate to have DC provided to them on the inlet but they do a great job of eliminating DC on the outlet side. Then, it usually gets rectified anyway.

That's why I didn't suggest using an isolation transformer in front of the amp. Although it would probably solve the noise in the amp by eliminating DC to it, the iso tranny would be just as likely to hum. The problem might just be relocated. And I like iso trannys.

Should also mention that the reason you don't see a lot of the Channel Islands type of thing and why the DaBlok is DIY is because capacitors aren't intended for AC mains and there is a slight chance of the caps going "poof" or "bang". No, we're not talking dynomite here but it's scary enough for manufacturers. Thus, the heavy duty case, expensive components and the cost.

Have you gone to your breaker panel yet and turned off everything except the wall outlets to the stereo? Unpugged the TV cable and any dimmers or 2 or 3-way lights? You might find the source of the DC is something that seems completely unrelated.

Tvad is right, there are other causes for noise besides DC but I'm stickin' to my story unless you prove me wrong. Maybe even after that.
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